1. Field of the Invention
The invention relates to attitude indicator systems and in particular to novel apparatus for indicating attitude failure within said systems.
2. Description of the Prior Art
Different approaches have been utilized to indicate attitude failure, usually due to a loss of power, in an attitude indicator system. One such method is described in U.S. Pat. No. 2,613,352 entitled "Radio Navigation System." In that system, the pointers normally utilized to indicate the attitude of the aircraft, are equipped with flags labelled OFF which appear when power is lost. The flags are controlled by relays supervising the power supply for the system.
In order to insure recognition of the attitude, an additional indication is ordinarily provided. Typically, this additional indication has consisted in rotating a spherical member of the attitude indicator system, such as that described in U.S. Pat. No. 2,737,640 entitled "Aircraft Navigation Instrument," substantially about its roll axis. The spherical member is weighted in a manner so that, as power is removed from the system, the gravitational pull of the weight rotates the spherical member through an angular displacement of 60 to 90.degree.. However, weighting does not prove to be practical for attitude indicator systems in which the roll servmomotor, which governs the rotation of the spherical member about its roll axis through a gear train, has substantial drag or where there is appreciable friction in the gear train.
A method is needed which, as in the instances of the prior art mentioned, does not require additional panel space, and which is economical, adaptable to a variety of systems, and which has minimal power requirements during quiescent operating conditions.